This invention relates to a special purpose computer system and more particularly to a computer system for both creating and emulating control read only memories for use in conjunction with programmable calculators and the like.
1. Field of the Invention
The Control Read Only Memory (CROM) development system operates as two independent, yet integrated, systems. First, the system generates programmable calculator keycodes from source code entered via the systems computer keyboard, then maps the code into the systems read/write random access memory in CROM format, and generates a Gate Placement Tape, such as contained within a cassette, from data stored in that memory. Secondly, the system emulates a CROM for real time interconnection to the programmable calculator. The data stored in the system memory is presented to the prgrammable calculator in the same manner as such data would be presented from a CROM, and the calculator executes and responds to the data as though the actual CROM were present within it, thereby allowing actual in-calculator testing of the generated keycodes prior to commitment of the code to masks and permanent CROMs manufactured. The CROM is a 5000 by 8 bit word calculator pre-programmed storage module used as an interchangeable addition to the programmable calculator's limited read/write memory. While many standard CROM program modules are offered, custom programs are often required by users, and provided as a custom code version of a standard Texas Instruments TMCO540 CROM. Due to the programmable calculator's limited read/write program memory storage capacity, in-calculator testing of CROM software is not possible by direct program loading due to inadequate storage.
2. Description of Prior Art
Computer system translation of keyboard entered source keycode data to CROM object code utilizing a CROM assembler, subsequent translation to a compatible Gate Placement format output, and storage on an external tape storage medium are steps utilized in the CROM development flow. Heretofore, these steps were performed as subtasks of a general purpose computer system, with the resulting Gate Placement Tape being transported to the mask generation facility, and transformed into prototype CROM masks which in turn produced prototype CROMs for actual in-calculator software debugging. Alternately, a programmable calculator could be simulated in software in the general purpose computer system and the CROM object code executed under control of the simulation program. However, this process is slow, costly and inaccurate, and only provides a partial testing of CROM object code prior to commitment to prototype CROM parts. The use of prototype CROMs for final in-calculator program debugging is costly in time and money.